1. Field of the Invention
The present invention relates, in general, to the building panel art, and more particularly, to the art of manufacturing and mounting on buildings, an exterior facade formed of integrally joined thin granite or marble.
2. Description of the Prior Art
In the past, several methods have been employed to provide a building structure, such as a skyscraper, with a facade of a selected facing material such as marble or granite. Although each of the methods was moderately successful, each had inherent weight or structural disadvantages which the present invention has overcome.
In an early construction method, selected pieces of facing material of marble or granite were handset directly on the structural steel skeleton or poured concrete structure of the building and held thereto by bolts or the like. In this construction, the panels of the stone facing material were required to be at least several inches thick in order to have the strength to support their own weight without cracking. Such thick panels were both costly to make and difficult to handle if made with a desirably large height and width to speed covering of the building surface. If panels having small height and width dimensions were used, an increased number of panels were required to cover a building surface, thus also increasing the number of time-consuming panel mounting operations required.
A later method of attaching granite or marble facing to a building is shown in Castellarin, U.S. Pat. No. 3,724,152 to include backing the selected architectural grade facing material with a supporting member of a suitable hard stone such as marble or granite and then backing this stone with a layer of conventional concrete. The facing material and its stone and concrete backing were then fastened to the building structure by suitable fastening means such as bolts. In this method, relatively thin panels of a facing material were used, but the stone and concrete backing itself was required to have a great weight and thickness in order to support its own weight, and the weight of the panel, without cracking.
Bourke, U.S. Pat. No. 3,723,233, shows a marble faced composite wall panel comprising a marble lamina bonded by an adhesive to a backing. The backing is a structure of metal honeycomb skinned with a layer of glass fiber. Bourke, U.S. Pat. No. 3,963,846, replaces the structure of metal honeycomb of the '233 patent with a multi-cellular paper core. The core consists of a honeycomb structure of phenolic resin impregnated paper in the form of a sheet, with individual cells extending perpendicularly to the planes of both the sheet and the marble lamina. Adhesive bonding of stone panels and non-stone backing material are peculiarly subject to unbonding caused by differences in the expansion coefficients of the materials when subjected to the effects of the sun or cold temperatures after mounting on a building.
Martin, U.S. Pat. No. 3,885,008, while not relating to the cladding of buildings with marble or granite, discloses a prefabricated wall panel which is molded as a unit for mounting on wood frame buildings.
As will be discussed more fully below, the present invention overcomes the inherent weight and structural limitations of the prior art, by overlaying the back of a number of pre-sized panels of a selected facing material such as marble or granite, having anchor means, partially disposed therewithin, with a relatively thin, sprayed-on layer of fiberglass-strengthened concrete backing. The resulting building panel is then adapted to be secured to a building structure by suitable fastening means secured to a plurality of integral, concrete support ribs formed upon the rear surface of the building panel.